A 12-year-old boy is brought to the office by his mother due to skin bruising, muscle aches, and fatigue. She is concerned that these symptoms are due to him being bullied at school, which the boy denies. He has also had significant nausea over the last week but has maintained adequate oral intake. The patient has no chronic medical conditions. Examination reveals mucosal pallor and numerous ecchymoses on the bilateral extremities. Laboratory results are as follows: Peripheral blood smear reveals significant immature myeloid cells. Which of the following is the most likely underlying cause of this patient's acute renal failure?

Question

A 12-year-old boy is brought to the office by his mother due to skin bruising, muscle aches, and fatigue.  She is concerned that these symptoms are due to him being bullied at school, which the boy denies.  He has also had significant nausea over the last week but has maintained adequate oral intake.  The patient has no chronic medical conditions.  Examination reveals mucosal pallor and numerous ecchymoses on the bilateral extremities.  Laboratory results are as follows:  Peripheral blood smear reveals significant immature myeloid cells.  Which of the following is the most likely underlying cause of this patient's acute renal failure?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d72f_97d3_bc81_ef8af880401d_MD0003_00 This boy's hematologic findings of anemia (eg, fatigue, pallor), thrombocytopenia (eg, ecchymoses), and leukocytosis with immature myeloid forms suggest acute myelogenous leukemia (AML). Concurrent hyperkalemia, hyperuricemia, elevated lactate dehydrogenase (LDH), and acute kidney injury (AKI) (with resultant acidosis) raises suspicion for spontaneous tumor lysis syndrome (TLS). Although most cases of TLS occur following initiation of cytotoxic chemotherapy, some hematologic malignancies (eg, AML) with high tumor cell burdens or rapid replication rates can cause TLS in the absence of chemotherapy due to massive, spontaneous tumor cell lysis. TLS is marked by the release of intracellular tumor contents into the bloodstream, leading to: Hyperuricemia: purine nucleic acids from lysed tumor cells are metabolized by xanthine oxidase to uric acid. Because uric acid is poorly soluble in urine, patients often develop obstructing uric acid stones in the renal tubules, which causes AKI. Hyperphosphatemia: tumor cells frequently contain >3 times more intracellular phosphate than healthy cells. Phosphate (renally excreted) binds calcium in the renal tubules and forms obstructing calcium-phosphate stones; this can also cause AKI and leads to systemic hypocalcemia. Hyperkalemia: intracellular potassium is released into the circulation, which can cause cardiac arrhythmias. Other common manifestations of TLS include nausea, vomiting, myalgia, and fatigue. Aggressive intravenous hydration, uric acid reduction (eg, rasburicase, allopurinol), and treatment of electrolyte abnormalities is required to prevent long-term sequalae and death. (Choices A and C) Multiple myeloma (MM) frequently causes AKI due to obstructing light-chain casts; in some cases of MM, renal failure may be due to concurrent amyloidosis. Although hematologic abnormalities (eg, normocytic anemia, thrombocytopenia) can be seen with MM and amyloidosis, these conditions are very rare in children, do not typically cause significant hyperuricemia, and would not explain immature myeloid cells on peripheral smear. (Choices B, D, and F) Interstitial nephritis is typically associated with concurrent medication use (eg, trimethoprim-sulfamethoxazole), infection, or rheumatologic disease. Proliferative glomerulonephritis can be seen in certain solid organ malignancies. Urethral obstruction can impair urinary excretion. Although these conditions can cause AKI, the elevated uric acid and LDH levels and the immature myeloid forms make spontaneous TLS far more likely. Educational objective: Spontaneous tumor lysis syndrome can occur in patients who have hematologic malignancies with high tumor burden or rapid replication rate. It typically presents with acute kidney injury due to the formation of uric acid and calcium-phosphate stones and/or complications (eg, cardiac arrhythmia) from hyperkalemia. References: Hematological malignancies presenting as spontaneous tumor lysis syndrome: a case series. (http://www.ncbi.nlm.nih.gov/pubmed/30598972)

A 12-Year-Old Boy Is Brought to the Office by His